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This Collective Article presents information on 20 taxa belonging to five (5) Phyla: Cnidaria (2), Mollusca (8), Arthropoda (4), Echinodermata (1) and Chordata (5) recorded from the Alboran Sea to the Levantine Sea. These new records were found in seven (7) different ecoregions as follows: Alboran Sea: new record of the rare football octopus Ocythoe tuberculata in the harbour of Algeciras (Spain) ; Western Mediterranean Sea: first record of the isopod Arcturinella deltensis in the Ligurian Sea, and the third 969Medit. Mar. Sci., 23/4 2022, 968-994in the whole Mediterranean Sea ; third Mediterranean site for the MuricidaeCoralliophila ahuiri along the Italian coasts (Alghe-ro) ; first and westernmost record of the goby Corcyrogobius liechtensteini from the Iberian Peninsula ; new record of the sea slug Glaucus atlanticus from the coast of the Iberian Peninsula ; first and easternmost record of Holothuria (Vaneyothuria) lentiginosa lentiginosa along the Italian coasts ; Tunisian Plateau/Gulf of Sidra: seventh record of the oceanic squid Thysanoteuthis rhombusin Tunisia, and first for the Gulf of Gabes. Ionian Sea: second occurrence of the Atlantic tripletail Lobotes surinamensis in the Ionian Sea and first record from the Strait of Messina area ; new record of the rare sea elephant Pterotrachea coronata from the Strait of Messina ; Adriatic Sea: first record of a facies of football ascidian Diazona violacea in the South Adriatic Sea (Tremiti Island, Italy) ; two records of the sevengill shark Heptranchias perlo in Croatian waters after more than 70 years of absence of documented records in this area ; first known occurrence of the nudibranch Jalonus hyalinus in Slovenian waters and also the first known occurrence of this species in the Adriatic Sea ; first record of the nudibranch Okenia elegans in Slovenian waters ; Aegean Sea: First record of the parasitic isopod Nerocila milesensis along Greek coasts (Crete island) as well as the second record world-wide ; additional record of the brachyuran Paragalene longicrura collected from the Saronikos Gulf (Greece) ; first record of the siphonophore Rhizophysa filiformis in Greek waters as well as the second record of this species in the eastern Mediterranean basin ; new record of the rare and protected angelshark Squatina aculeata along Turkish coasts ; Levantine Sea: first record of the marine amphipod Caprella andreae in the Levantine Mediterranean shore of Israel, based on both morphological and molecular data ; first occurrence of the cephalopod Tremoctopus violaceus along Turkish coasts, which confirms its presence in the north-eastern coasts of Turkey ; record of a bloom of the thermophilic jellyfish Pelagia noctiluca in the north Levantine Sea.

The analysis of 879 ROV dives carried out along the Italian coasts on hard substrata at mesophotic and upper bathyal depths (40-775 m) allowed us to evaluate the current basin-scale presence, relative abundance, bathymetric limits, and habitat preferences of one of the most charismatic Mediterranean habitat-former anthozoan species, Corallium rubrum (Linnaeus, 1758). The species is widespread, and its occurrence ranged from 13% of the explored sites in Ionian Calabria to a hotspot of approximately 80% in Sardinia. Population relative densities were generally low (< 10 colonies m-2), except along the Sardinian coasts and in some areas along the Apulian coast. Almost no red coral colonies were observed between 60 m and 590 m in the nine explored offshore seamounts in the Ligurian and Tyrrhenian Seas. A distinctive coastal distribution discontinuity was found in the Ionian Sea. The optimum bathymetric distribution was between 75 m and 125 m, and no colonies were found below 247 m. Red coral colonies showed a preference for biogenic habitats dominated by crustose coralline algae (CCA) and vertical substrata. The species was absent on iron wrecks. Corallium rubrum disappeared from 14% of the historical fishing banks, while it was confirmed in 86% of them, some of which have been deeply harvested in the past. In particular, the still flourishing Sardinian populations could be supported by the high reproductive potential and favourable hydrodynamic conditions in the area.

Detailed knowledge about the distribution of species in need of protection is required for the management of Marine Protected Areas, a major tool to reduce marine biodiversity loss. Such knowledge is deficient for most marine invertebrates. Axinella polypoides is a marine sponge included on the list of protected species by the Barcelona Convention (1976) and the Bern Convention (1987). This large and erect species has an important ecological role in habitat forming and benthic–pelagic coupling. Bathymetrical, geographical and ecological data over the last 60 years were collated from publications and reports, together with new surveys to assess the distribution and protection status in Liguria of A. polypoides. It identified a more widespread distribution than previously thought, which points at a general need for dedicated investigations on the occurrence of species that require protection. Bathymetrical distribution was trimodal, with peaks corresponding to different geomorphological settings: coastal cliff bases (around 38 m depth), inner shelf shoals (52 m) and rocks amidst coarse sediment on the outer shelf (79 m). Density was significantly greater at the shallowest depths. The species was mostly found in the coralligenous biocoenosis, in association with other characteristic species or forming a monospecific facies. On (sub)vertical cliffs, A. polypoides often exhibited an unusual cane shape, rather than the typical bushy morphology, thus causing confusion with the congeneric A. cannabina, a more southern species. Records of the latter in the Ligurian Sea therefore need confirmation. Only a minority (22.6%) of A. polypoides records were in Marine Protected Areas, the remainder being located in areas with no current environmental protection plans in place. While the occurrence of this species in MPAs remained stable over the decades, the only quantitative historical data available indicated that populations in non‐protected areas were declining owing to anthropogenic impacts (fishing and anchoring).

23 pages, 21 figures, 3 tables, This Collective Article presents information about 21 taxa belonging to seven Phyla (one Ochrophyta, one Porifera, three Cnidaria, two Arthropoda, three Mollusca, one Echinodermata, and ten Chordata) and extending from the western Mediterranean Sea to the Levantine Sea. The new records were reported from nine countries as follows: Spain: first records of three deep-sea species from the Blanes Canyon along the Catalan margin, namely the gorgonian Placogorgia coronata, the bivalve Acesta excavata, and the Azores rockling Gaidropsarus granti; Italy: first record of the mesopsammic nudibranch Embletonia pulchra from Ligurian shallow-waters; first record of the deep-sea carnivorous sponge Lycopodina hypogea from the north-central Tyrrhenian Sea, living in dense clusters over dead black corals; new records of the Portuguese man o’ war Physalia physalis from Sardinian and Sicilian waters; first Italian record of the large asteroid Coronaster briareus from the Ionian Sea; first record of the white grouper Epinephelus aeneus in the northernmost point of the Adriatic Sea; Croatia: first record of the gastropod Haliotis mykonosensis for the Adriatic Sea; Malta: new sightings of Physalia physalis from Maltese waters; Libya: first record of the sand crab Albunea carabus from two localities along the Libyan coast; Greece: first records of the deep-sea black coral Parantipathes larix from the eastern Mediterranean Sea; first verified record of the agujon needlefish Tylosurus imperialis in the Hellenic Ionian Sea; first confirmed record of the brown algae Treptacantha squarrosa in the eastern Mediterranean Sea; new records of three deep-sea fish species from the Aegean Sea, namely the bluntnose sixgill shark Hexanchus griseus, the Atlantic pomfret Brama brama, and the rudderfish Centrolophus niger; new record of the tripletail Lobotes surinamensis from Lesvos Island; new record of the shrimp Brachycarpus biunguiculatus from the gut content of the non-indigenous lionfish Pterois miles; Turkey: new record of the imperial blackfish Schedophilus ovalis from Turkish waters; Lebanon: first record of the slender sunfish Ranzania laevis, stranded along the Lebanese coast; Israel: new record, after about 60 years from the last catch, of the spotted dragonet Callionymus maculatus, Their studies presented in this Collective Article received funding from the Spanish Ministry of Science and Innovation (ABRIC Project, Ref. RTI2018-096434-B-I00). The study by Bo et al. was funded by EU-ENPI CBC MED 2007–2013, “Ecosystem conservation and References sustainable artisanal fisheries in the Mediterranean basin” (ECOSAFIMED) (grant number ECOSAFIMED - Abushaala, N.M., Shaibi, T., Howaege, H.M., 2014. The abun-II-B/2.1/1073), With the funding support of the ‘Severo Ochoa Centre of Excellence’ accreditation (CEX2019-000928-S), of the Spanish Research Agency (AEI)

Litter has become a common component of marine ecosystems, and its assessment and monitoring are now of primary interest. Here, we characterized seafloor litter in the mesophotic depth range of the Ligurian Sea, one of the most urbanized basins of the Mediterranean Sea. Eighty sites (30–220 m depth) were investigated by by means of ROV video transects. Data regarding environmental parameters and anthropic pressures were used to explain the distribution of human-derived objects. Litter resulted widely distributed in all the investigated areas, with maximum densities of 7900 items ha−1. It was mainly represented by abandoned fishing gears, with highest abundances found on the deep coastal rocky shoals exploited by artisanal and recreational fishermen. Urban litter, primarily represented by plastics, was generally higher close to shore, especially near river mouths and large harbors. Litter densities reported here are among the highest ever recorded in Europe, denoting the urgency for specific actions to prevent further spreading.

This study presents a description of Bispira riccardi sp. nov., a new habitat-forming sabellid polychaete from the mesophotic NW Mediterranean Sea. Individuals, up to 20 cm long, show a peculiar morphology of radioles, thoracic uncini, companion chaetae and ventral shield of the collar. The phylogenetic position of this new taxon in the genus Bispira has been validated using nuclear (18S rRNA) and mitochondrial (COI) markers. Aggregations of B. riccardi sp. nov. were found by ROV on horizontal muddy bottoms between 56 and 85 m, in areas subjected to high trophic inputs. Patches are fragmented and dense (up to 943 individuals m 2) probably accounting for various hectares. A 5-days continuous monitoring, carried out using an autonomous lander, revealed that the contraction of the branchial crown was positively affected by temperature and current, rapidly responding to meteorological events. The filtering activity and high density of these fields suggest a considerable impact on the pelagic-benthic coupling and the amount of organic matter in the sediments. Indeed, meiofaunal abundance and diversity within the aggregations resulted significantly higher than in outer stations. These findings highlight the undisclosed potential of the deep Mediterranean Sea for sabellid diversity and their importance as habitat-forming species on mesophotic soft bottoms.

The Ligurian Sea is one of the most studied Mediterranean basins. Since the beginning of the last century, many research expeditions have characterized its benthic and pelagic fauna through scuba diving and trawl surveys. However, a large knowledge gap exists about the composition of benthic communities extending into the so-called mesophotic or twilight depth range, currently under intense pressure from commercial and recreational fishing. A series of visual surveys, carried out by means of remotely operated vehicles between 2012 and 2018, were conducted along the Ligurian deep continental shelf and shelf break, between 30 and 210 m depth, in order to characterize the main benthic biocoenoses dwelling at this depth range and to determine the most relevant environmental factors that explain their spatial distribution. Deep circalittoral communities of the Ligurian Sea were represented by a mixture of species belonging to the deepest extension of shallow-water habitats and deep circalittoral ones. Twelve major biocoenoses were identified, each one characterized by specific preferences in depth range, substrate type and seabed slope. Those biocoenoses included gorgonian and hydrozoan forests, dense keratose sponge grounds, Dendrophyllia cornigera gardens, bryozoan beds and soft-bottom meadows of sabellid polychaetes and soft-corals. Other less common aggregations included six forests of black corals and two populations of Paramuricea macrospina. A georeferenced database has been created in order to provide information to managers and stakeholders about the location of the identified communities and high-diversity areas, aiming to facilitate sustainable long-term conservation of the Ligurian benthic ecosystem.

Temperate mesophotic reefs (circalittoral and offshore circalittoral hard/firm habitats), host complex three-dimensional animal forests and are vulnerable habitats protected by international agreements. In order to evaluate and monitor the environmental status of these ecosystems, the multi-parametric index Mesophotic Assemblages Conservation Status (MACS) was developed, including two independent components, namely Index of Status (Is) and Index of Impact (Ii). The Is includes six metrics, targeting conspicuous species diversity, basal layer and canopy composition, whilst the Ii is composed by six metrics targeting siltation level, canopy condition and marine litter occurrence. Underwater video transects recorded with a Remotely Operated Vehicle (ROV) along the Ligurian and Tyrrhenian Seas offered the chance to test the index on a large geographic scale and various ecological settings, for a total of 14 sites subjected to different human pressures. MACS index showed a high potentiality to distinguish among a wide range of environmental conditions, with local critical situations mainly related to high fishing pressure. With respect to other existing indices, MACS is based on a larger number of parameters, resulting in a higher ability to disentangle natural and anthropogenic factors, hence it leads to a better interpretation of local situations. This tool represents a contribution to the requirements for the monitoring of these marine environments, set by the EU Marine Strategy Framework Directive, the Habitats Directive, and the guidelines of the Integrated Monitoring and Assessment Programme of the Mediterranean Sea and Coast of the Barcelona Convention.